The MPLS WG Archive

["Osama Farrag" <ofarrag@mantaronetworks.com>]

Assume the following Network topology

                                 +--------+
                                 |        |
                                 |        |
                         --------|    I1  |
                        /        |        |
                       /         +--------+
                      /
+------+          +-------+       +-------+
|      |          |       |       |       |
| E1   |----------|  C1   |-------|  I2   |
|      |          |       |       |       |
+------+          +-------+       +-------+
                      \
                       \          +-------+
                        \         |       |
                         ---------|  I3   |
                                  |       |
                                  +-------+


If LER I2 initiates an LSP to E1 using RSVP-TE path message,  with SE bit
set. Then at later point in time LER I1, initiates RSVP LSP tunnel to E1
with SE bit set and same TUNNEL-ID value used by I2 in session object.

A- When the second Path message arrive at E1; assume E1 supports SE style,
Does E1 required to assign a new MPLS label in RSVP response message? or
send the same label used in the previous message?

B- What should happen at C1;

First: when the second Path message is received from I1, should it pass thru
to E1? if not then point A is not an issue, But then C1 must respond with
RESV message and assign a LABEL to I1. I think  RESV must be initaited from
the EGRESS LER.

Second: If C1 passes the Second path message thru to E1, then when it
receives RESV message from E1 and SE bit set, I assume it will merge the
LSPs from I1 and I2. If a new Label is assigned by E1 which Label C1 should
use for traffic bound for E1, can it continue to use them both and refresh
them. I think that C2 must maintain both labels and merge action at C1 only
implies that resevered resources are shared but these two LSPs that are
associated by TUNNEL-ID?


Regards
Osama Farrag



What happens at C2; does CE merges the two LSPs?


>-----Original Message-----
>From: owner-mpls@UU.NET [mailto:owner-mpls@UU.NET]On Behalf Of David
>Charlap
>Sent: Monday, February 04, 2002 11:44 AM
>To: rsvp-te
>Subject: Re: question on reservation styles
>
>
>Subhakar K S wrote:
>>
>> In RSVP, how does the egress node decide on which
>> reservation style to use.
>
>In classical RSVP, there is no way for it to know.  The choice is beyond
>the scope of RSVP.
>
>In RSVP-TE, the ingress node can request SE style by setting the
>appropriate bit in the SESSION_ATTRIBUTE object.  If this bit is set,
>then SE style should be used.  If SESSION_ATTRIBUTE is present and this
>bit is not set, then FF style should be used.
>
>If SESSION_ATTRIBUTE is not present, then the switch is free to use
>either.
>
>Of course, all of the values in SESSION_ATTRIBUTE are advisory, so an
>egress router is free to ignore the bits and choose whatever style it
>wants, if there is a good reason to do so.  (Possible reasons include
>non-support of one style, explicit local policy.)
>
>-- David
>